dm: treewide: Rename ..._platdata variables to just ..._plat

Try to maintain some consistency between these variables by using _plat as
a suffix for them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/spi/pic32_spi.c b/drivers/spi/pic32_spi.c
index 463c13c..cd83c11 100644
--- a/drivers/spi/pic32_spi.c
+++ b/drivers/spi/pic32_spi.c
@@ -236,7 +236,7 @@
 			  const void *tx_buf, void *rx_buf,
 			  unsigned long flags)
 {
-	struct dm_spi_slave_platdata *slave_plat;
+	struct dm_spi_slave_plat *slave_plat;
 	struct udevice *bus = slave->parent;
 	struct pic32_spi_priv *priv;
 	int len = bitlen / 8;